Development of Oxide Dispersion Strengthened (ODS) Ferritic Steel Through Powder Forging
Oxide dispersion strengthened (ODS) ferritic steels are candidates for cladding tubes in fast breeder nuclear reactors. In this study, an 18%Cr ODS ferritic steel was prepared through powder forging route. Elemental powders with a nominal composition of Fe-18Cr-2 W-0.2Ti (composition in wt.%) with 0 and 0.35% yttria were prepared by mechanical alloying in a Simoloyer attritor under argon atmosphere. The alloyed powders were heated in a mild steel can to 1473 K under flowing hydrogen atmosphere. The can was then hot forged. Steps of sealing, degassing and evacuation are eliminated by using powder forging. Heating ODS powder in hydrogen atmosphere ensures good bonding between alloy powders. A dense ODS alloy with an attractive combination of strength and ductility was obtained after re-forging. On testing at 973 K, a loss in ductility was observed in yttria-containing alloy. The strength and ductility increased with increase in strain rate at 973 K. Reasons for this are discussed. The ODS alloy exhibited a recrystallized microstructure which is difficult to achieve by extrusion. No prior particle boundaries were observed after forging. The forged compacts exhibited isotropic mechanical properties. It is suggested that powder forging may offer several advantages over the traditional extrusion/HIP routes for fabrication of ODS alloys.
Keywordsforging isotropy mechanical alloying mechanical properties ODS steel powder metallurgy
This research work was supported by the Board of Research in Nuclear Sciences, Government of India, Department of Atomic Energy (DAE) (Grant No. 2010/36/68-BRNS).
- 5.J.J. Fischer, Dispersion Strengthened Ferritic Alloy for Use in Liquid-Metal Fast Breeder Reactors (LMFBRS), U.S. Patent 4,075,010, 1978Google Scholar
- 10.M. Praud, F. Mompiou, J. Malaplate, D. Caillard, J. Garnier, A. Steckmeyer, and B. Fournier, Study of the Deformation Mechanisms in a Fe-14% Cr ODS Alloy, J. Mater. Sci., 2012, 428, p 90–97Google Scholar
- 20.Y. de Carlan, J.-L. Bechade, P. Dubuisson, J.-L. Seran, P. Billot, A. Bougault, T. Cozzika, S. Doriot, D. Hamon, J. Henry, M. Ratti, N. Lochet, D. Nunes, P. Olier, T. Leblond, and M.H. Mathon, CEA Developments of New Ferritic ODS Alloys for Nuclear Applications, J. Nucl. Mater., 2009, 386–388, p 430–432CrossRefGoogle Scholar
- 21.U. Prakash and V. Dabhade, A Process for Powder Forging of Metals/Alloys to Obtain Full Density Products, Indian Patent Application No. 3270/DEL/2015, 12 Oct 2015.Google Scholar
- 26.M. Inoue, T. Kaito, and S. Ohtsuka, Research and Development of Oxide Dispersion Strengthened Ferritic Steels for Sodium Cooled Fast Breeder Reactors Fuels, Materials Issues for Generation IV Systems, V. Ghetta, D. Gorse, D. Mazière, and V. Pontikis, Ed., Springer, Berlin, 2008, p 311–325 CrossRefGoogle Scholar